You should be able to get the B-12 and D adequately without seeing your doctor. They are super cheap at Sam’s Club or Costco.
Do you have any other symptoms or noted conditions?
I guess I could be trained to give myself shots at home if I pushed the matter. I’ve asked about it twice and they kind of brush me off saying most people go in to have a nurse administer it.
I found out about this deficiency when I started getting extreme dizzy/lightheaded spells, numb hips and legs after walking, and my speech was being affected, brain slow. Doc sent me to rule out heart condition, neurologist and checked blood levels to include B-12.